A sulfur defective Mn-doped Ni3S2–x nanosheet for enhanced overall water splitting

Non-precious and stable electrocatalysts towards both oxygen and hydrogen evolution reaction (OER/HER) are essential for effective overall water splitting in alkaline solution. In this study, a sulfur defective and manganese-doped nickel sulfide nanosheet that uniformly grown on nickel foam substrate (Mn–Ni3S2–x@NF) is synthesized. In alkaline solution, the Mn–Ni3S2–x@NF showed a low overpotential of 76 and 110 mV for OER and HER at 10 mA cm−2, respectively, together exhibiting excellent stability for both OER and HER reaction. It was confirmed by the experimental results that sulfur defects and Mn-doping synergistically optimized the electronic structure of Mn–Ni3S2–x with increased electrical conductivity and enhanced OER/HER activity. Moreover, amorphous nickel oxyhydroxide (NiOOH) was observed by in situ Raman during the OER condition, suggesting NiOOH is the active phase for OER reaction. Furthermore, the electrolyzer assembled by Mn–Ni3S2–x@NF merely needs 1.46 V to reach 10 mA cm−2 and shows good stability as well. This study provides a feasible way to prepare high-efficiency bifunctional catalysts for overall water splitting.